如何串行链接http请求函数

Question

我需要按顺序依次从三个 http 请求中获取响应。

我能够使用嵌套函数来做到这一点。我还需要使用全局范围内最后一个请求的响应，这是我无法使用嵌套解决方案实现的。

var request = require("request");

httpRequest1((getRequest1) => {
  console.log(getRequest1);
  httpRequest2((getRequest2) => {
    console.log(getRequest2);
    httpRequest3((getRequest3) => {
      console.log(getRequest3);
    });
  });
});

function httpRequest1 (callback){
var options = { method: 'POST',
  url: };
request(options, function (error, response, body) {
  if (error) throw new Error(error);
  callback (body);
});}

function httpRequest2(callback){
var options = { method: 'POST',
  url:  };
request(options, function (error, response, body) {
  if (error) throw new Error(error);
  callback(body);
});}

function httpRequest3(callback){
  var options = { method: 'POST',
    url: };
  request(options, function (error, response, body) {
    if (error) throw new Error(error);
    callback(body);
  });}

Answer 1

您应该考虑更现代的 async/await 模式并使用它来解决承诺。它将使您的代码对您自己和其他人更具可读性。

阅读此博客了解更多详情，特别是您案例中的 "Chaining Operations" 部分：https://www.sitepoint.com/simplifying-asynchronous-coding-async-functions/

Answer 2

function httpRequest1 (callback){
    var options = { method: 'POST', url: };
    return new Promise(function (resolve, reject) {
       request(options, function (error, response, body) {
         if (error) return reject(error);
        resolve(body);
       });
   });
}

function httpRequest2 (callback){
    var options = { method: 'POST', url: };
    return new Promise(function (resolve, reject) {
       request(options, function (error, response, body) {
         if (error) return reject(error);
        resolve(body);
       });
   });
}

function httpRequest3 (callback){
    var options = { method: 'POST', url: };

   return new Promise(function (resolve, reject) {
       request(options, function (error, response, body) {
         if (error) return reject(error);
         resolve(body);
       });
   });
}

承诺

httpRequest1()
 .then(body1 => 

    return httpRequest2();
 )
 .then(body2 => 

      return httpRequest3();
 )
 .then(body3 => 

 ).catch(error => {
     // error code
} );

Async/Await

function async getResponse() {
  try {
    const body1 = await httpRequest1();
    const body2 = await httpRequest2();
    const body3 = await httpRequest3();
  } catch (e) {
     console.log(e);
  } 
}

已更新

Await 在正常功能下不起作用。如果使用 await，则必须在 asyn 函数中使用它。如果你想从普通函数调用序列化异步函数，那么 promise 是更好的选择。但你可以使用另一种方式。假设我们有一个像上面那样的异步函数，其中 return of response

function async getResponse() {
  try {
    const body1 = await httpRequest1();
    const body2 = await httpRequest2();
    const body3 = await httpRequest3();
    return { body1, body2, body3 }
  } catch (e) {
     console.log(e);
  } 
}

function normalFunction() {
    //  const res  = getResponse(); it will not work

    getResponse()
    .then(result  => {
      // you will get the result here
    })


}

后台异步函数 return promise Result 。这就是为什么我们可以这样写。

Answer 3

var request = require("request-promise");
( async () => {
    const getRequest1 = await httpRequest1();
    const getRequest2 = await httpRequest2();
    const getRequest3 = await httpRequest3();
})();

async function httpRequest1() {
    var options = {
        method: 'POST',
        url: ''
    };
    const body = await request(options)
    if (!body) throw "error";
    return body;
}

async function httpRequest2() {
    var options = {
        method: 'POST',
        url: ''
    };
    const body = await request(options)
    if (!body) throw "error";
    return body;
}

async function httpRequest3() {
    var options = {
        method: 'POST',
        url: ''
    };
    const body = await request(options)
    if (!body) throw "error";
    return body;
}

Answer 4

如果请求是独立的，可以使用Promise.all()。在调用httpRequest2等之前，您不必等待httpRequest1的响应。

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all

如何串行链接http请求函数

How to chain http request functions in serially

node.js

asynchronous

chaining